The overall goals of this proposal are to study the levels and regulation of steroid receptors in endocrine-responsive tumors and thus to improve the therapy of these tumors with steroids, to develop and advance the use of antisteroids, and to evaluate treatments that might prevent muscle wasting that occurs in the tumor-bearing host. The specific objectives are: (1) to relate the response to therapy with steroids to the endogenous and regulated levels of steroid receptors in estrogen-dependent and -independent mammary tumors; (2) to initiate steroid receptor studies and therapeutic trials with the transplantable androgen-dependent rat tumor R-3327; (3) to stimulate the development of antisteroids for use in the treatment of endocrine-responsive tumors; (4) to correlate chemical structure and biological activity of steroid analogues with particular emphasis on analogues of progesterone and other progestins; (5) to study the basis for resistance of lymphoid tumors to glucocorticoids and other endocrine tumors to steroid therapy; and (6) to explore the possibility that androgen or progesterone analogues, by competing with glucocorticoids for receptors in muscle, can alleviate muscle wasting in advanced cancer.